CH32 USB Implementation

CH32 has three USB device controllers, listed below.
For devices with a hardware Unique ID (UID) such as CH32V2/V3, it is recommended to derive the USB device serial number from the chip UID and pass it to the USB device constructor as a {pointer, length} pair.

Controller	Class	Role	Notes
USB_DEVICE_FS	LibXR::CH32USBDeviceFS	Device	FSDEV device path
USBFS/OTG FS	LibXR::CH32USBOtgFS	Device side of OTG FS	OTG FS device path
USBHS/OTG HS	LibXR::CH32USBOtgHS	Device side of OTG HS	OTG HS device path

Note: On common CH32V2/V3 parts, the UID is 96 bits (12 bytes) and can be read from 0x1FFFF7E8 as a contiguous 12-byte block.

CH32USBDeviceFS (FSDEV)

CH32USBDeviceFS supports two endpoint declaration styles. The first entry is EP0, and the following entries are numbered in order from EP1. A buffer size of 128 bytes is recommended for non-EP0 endpoints:

1. {ep1_buffer}: bidirectional endpoint; the buffer is split in half into OUT (first half) and IN (second half); the EP0 entry is not split
2. {ep2_buffer, true}: unidirectional endpoint; the whole buffer belongs to that direction (true for IN, false for OUT)

LibXR::CH32USBDeviceFS usb_dev(
    /* EP */
    {
        {ep0_buffer},
        {ep1_buffer},
        {ep2_buffer},
    },
    /* packet size */
    LibXR::USB::DeviceDescriptor::PacketSize0::SIZE_64,
    /* vid pid bcd */
    0x1D50, 0x6199, 0x0100,
    /* language */
    {&LANG_PACK_EN_US},
    /* config */
    {{&cdc1}},
    /* Serial Number UID (address and length of the raw CH32 UID bytes) */
    {reinterpret_cast<void*>(0x1FFFF7E8), 12});

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CH32USBOtgFS (OTG FS)

CH32USBOtgFS supports the following endpoint declaration styles; endpoint numbers increase in order from EP0.

1. {ep0_buf_fs}: declare the EP0 buffer
2. {ep1_in_buf_fs, true}: declare a unidirectional IN endpoint
3. {ep2_out_buf_fs, false}: declare a unidirectional OUT endpoint
4. {ep3_shared_buf_fs}: declare a bidirectional endpoint that shares one buffer entry

LibXR::CH32USBOtgFS usb_dev_fs(
    /* EP */
    {
        {ep0_buf_fs},
        {ep1_in_buf_fs, true},
        {ep2_out_buf_fs, false},
        {ep3_shared_buf_fs},
    },
    /* packet size */
    LibXR::USB::DeviceDescriptor::PacketSize0::SIZE_64,
    /* vid pid bcd */
    0x1D50, 0x6199, 0x0100,
    /* language */
    {&LANG_PACK_EN_US},
    /* config */
    {{&cdc_fs}},
    /* Serial Number UID (address and length of the raw CH32 UID bytes) */
    {reinterpret_cast<void*>(0x1FFFF7E8), 12});

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CH32USBOtgHS (OTG HS)

CH32USBOtgHS supports three endpoint declaration styles. For non-EP0 endpoints, a buffer size of 1024 bytes is recommended. Endpoint numbers auto-increment:

1. {ep0_buffer_hs}: pass the EP0 buffer directly.
2. {ep1_buffer_tx_hs, true}: pass the buffer and enable double buffering
   • ep1_buffer_tx_hs: buffer for the EP1 endpoint
   • true: whether this endpoint is configured as IN
3. {ep2_buffer_tx_hs, ep2_buffer_rx_hs}: pass the IN (tx) and OUT (rx) buffers of a bidirectional endpoint without enabling double buffering

LibXR::CH32USBOtgHS usb_dev_hs(
    /* EP */
    {
        {ep0_buf_hs},                    // EP0
        {ep1_in_buf_hs, true},           // EP1 IN (unidirectional, double-buffered)
        {ep2_out_buf_hs, false},         // EP2 OUT (unidirectional, double-buffered)
        {ep3_in_buf_hs, ep3_out_buf_hs}  // EP3 bidirectional (IN first, then OUT; no double buffer)
    },
    /* vid pid bcd */
    0x1D50, 0x6199, 0x0100,
    /* language */
    {&LANG_PACK_EN_US},
    /* config */
    {{&cdc2}},
    /* Serial Number UID (address and length of the raw CH32 UID bytes) */
    {reinterpret_cast<void*>(0x1FFFF7E8), 12});

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